The present invention relates to an improved mix of carbon aggregate and binder. More particularly, it relates to a seam mix useful for forming fluid-tight, electrically conductive seams between carbon blocks in the bottom of a Hall-Heroult cell for producing aluminum metal by the electrolysis of Al.sub.2 O.sub.3.
Background material on the technique of using seam mixes in the construction of Hall-Heroult cells is given in U.S. Pat. No. 2,378,142 issued June 12, 1945, to Hurter for a "Method For Making Furnaces For the Electrolytic Production of Aluminum" and in U.S. Pat. No. 3,576,700 issued Apr. 27, 1971, to M. B. Dell for "High Strength Joined Porous Block Structure and Method of Making Same". The seams are referred to in the Hurter patent as "interspaces".
According to a present method of seam mix usage in the construction of Hall-Heroult cells, prebaked cathode blocks of carbon are arranged in a cell bottom, separated by seams 1 to 3 inches wide. To obtain optimum properties, e.g. high density, in the seam, conventional practice has been to preheat the carbon blocks to 60.degree. to 130.degree. C., with hot, for example 130.degree. C., seam mix then being incrementally tamped into the seams and between the cell side lining and the blocks to provide a smooth cell bottom.
This practice is disadvantageous for a number of reasons. Fumes are evolved from the heated mix. Considerable manpower and co-ordination are needed to achieve the placement of the hot seam mix between the heated blocks before the mix has had a chance to cool. The elevated temperatures mean discomfort for the people performing the work. And, significant capital and operating costs are associated with the preheating of both the blocks and the seam mix.